What Wavelength Goes With a Color? Contact Us What Wavelength Goes With a Color? Our eyes are sensitive to light which lies in a very small region of the electromagnetic spectrum labeled "visible light". This "visible light" corresponds to a wavelength range of 400 - 700 nanometers (nm) and a color range of violet through red. The human eye is not capable of "seeing" radiation with wavelengths outside the visible spectrum. The visible colors from shortest to longest wavelength are: violet, blue, green, yellow, orange, and red. Ultraviolet radiation has a shorter wavelength than the visible violet light. Infrared radiation has a longer wavelength than visible red light. The white light is a mixture of the colors of the visible spectrum. Black is a total absence of light. Earth's most important energy source is the Sun. Sunlight consists of the entire electromagnetic spectrum. Learn more: Violet Light The visible violet light has a wavelength of about 400 nm. Within the visible wavelength spectrum, violet and blue wavelengths are scattered more efficiently than other wavelengths. The sky looks blue, not violet, because our eyes are more sensitive to blue light (the sun also emits more energy as blue light than as violet).

The visible indigo light has a wavelength of about 445 nm. Blue Light The visible blue light has a wavelength of about 475 nm. Because the blue wavelengths are shorter in the visible spectrum, they are scattered more efficiently by the molecules in the atmosphere. This causes the sky to appear blue during the main part of the day, when blue light is scattered into your eye no matter which direction you look. Green Light The visible green light has a wavelength of about 510 nm. Grass, for example, appears green because all of the colors in the visible part of the spectrum are absorbed into the leaves of the grass except green. Green is reflected, therefore grass appears green. The visible orange light has a wavelength of about 590 nm. Low-pressure sodium lamps, like those used in some parking lots, emit a orange-ish (wavelength 589 nm) light. Red Light The visible red light has a wavelength of about 650 nm. At sunrise and sunset, the light you see has traveled a longer distance through the atmosphere. A large amount of blue and violet light has been removed as a result of scattering and the longwave colors, such as red and orange, are more readily seen.

There are many wavelengths in the electromagnetic spectrum the human eye cannot detect. Energy with wavelengths too short for humans to see Energy with wavelengths too short to see is "more violet than violet". Light with such short wavelengths is called "Ultraviolet" light. The term "ultra-" means higher than. How do we know this light exists? One way is that this kind of light causes sunburns. Our skin is sensitive to this kind of light. If we stay out in this light without sunblock protection, our skin absorbs this energy. After the energy is absorbed, it can make our skin change color ("tan") or it can break down the cells and cause other damage. Energy with wavelengths too long for humans to see Energy whose wavelength is too long to see is "redder than red". Light with such long wavelengths is called "Infrared" light. The term "Infra-" means "lower than". How do we know this kind of light exists? One way is that we can feel energy with these wavelengths such as when we sit in front of a campfire or when we get close to a stove burner.

Scientists like Samuel Pierpont Langley passed light through a prism and discovered that the infrared light the scientists could not see beyond red could make other things hot. Very long wavelengths of infrared light radiate heat to outer space. This radiation is important to the Earth's energy budget. If this energy did not escape to space, the solar energy that the Earth absorbs would continue to heat the Earth. Visible Light Waves RADIO WAVES | MICROWAVES | INFRARED | VISIBLE LIGHT | ULTRAVIOLET | X-RAYS | GAMMA RAYS Visible Light Waves Visible light waves are the only electromagnetic waves we can see. We see these waves as the colors of the rainbow. Each color has a different wavelength. Red has the longest wavelength and violet has the shortest wavelength. When all the waves are seen together, they make white light. When white light shines through a prism, the white light is broken apart into the colors of the visible light spectrum. Water vapor in the atmosphere can also break apart wavelengths creating a rainbow. Each color in a rainbow corresponds to a different wavelength of electromagnetic spectrum. How do we "see" using Visible Light? Cones in our eyes are receivers for these tiny visible light waves.

The Sun is a natural source for visible light waves and our eyes see the reflection of this sunlight off the objects around us. The color of an object that we see is the color of light reflected. All other colors are absorbed. Light bulbs are another source of visible light waves. This is an photograph taken from the space shuttle of Phoenix, Arizona. This is a true-color satellite image of Phoenix, Arizona. Can you see a difference between this image and the photo above it? There are two types of color images that can be made from satellite data - true-color and false-color. To take true-color images, like this one, the satellite that took it used sensors to record data about the red, green, and blue visible light waves that were reflecting off the earth's surface. The data were combined later on a computer. The result is similar to what our eyes see. Here is a false-color image of Phoenix. How does it compare to the true-color and space shuttle images on this page? A false-color image is made when the satellite records data about brightness of the light waves reflecting off the Earth's surface. These brightnesses are represented by numerical values - and these values can then be color-coded. It is just like painting by number!

The colors chosen to "paint" the image are arbitrary, but they can be chosen to either make the object look realistic, or to help emphasize a particular feature in the image. Astronomers can even view a region of interest by using software to change the contrast and brightness on the picture, just like the controls on a TV! Can you see a difference in the color palettes selected for the two images below? Both images are of the Crab Nebula, the remains of an exploded star! Here's another example - the below pictures show the planet Uranus in true-color (on the left) and false-color (on the right). The true-color has been processed to show Uranus as human eyes would see it from the vantage point of the Voyager 2 spacecraft, and is a composite of images taken through blue, green and orange filters. The false color and extreme contrast enhancement in the image on the right, brings out subtle details in the polar region of Uranus. The very slight contrasts visible in true color are greatly exaggerated here, making it easier to studying Uranus' cloud structure. Here, Uranus reveals a dark polar hood surrounded by a series of progressively lighter concentric bands.

One possible explanation is that a brownish haze or smog, concentrated over the pole, is arranged into bands by zonal motions of the upper atmosphere. What does Visible Light show us? It is true that we are blind to many wavelengths of light. This makes it important to use instruments that can detect different wavelengths of light to help us to study the Earth and the Universe. However, since visible light is the part of the electromagnetic spectrum that our eyes can see, our whole world is oriented around it. And many instruments that detect visible light can see father and more clearly than our eyes could alone. That is why we use satellites to look at the Earth, and telescopes to look at the Sky! This is a visible light image of Phoenix, Arizona, taken from the GOES satellite. We often use visible light images to see clouds and to help predict the weather. We not only look at the Earth from space but we can also look at other planets from space. This is a visible light image of the planet Jupiter. It is in false color - the colors were chosen to emphasize the cloud structure on this banded planet - Jupiter would not look like this to your eyes.

Visible Light and the Eye's Response Light Waves and Color - Lesson 2 - Color and Vision Visible Light and the Eye's Response Blue Skies and Red Sunsets As mentioned in the first section of Lesson 2 , our eyes are sensitive to a very narrow band of frequencies within the enormous range of frequencies of the electromagnetic spectrum. This narrow band of frequencies is referred to as the visible light spectrum. Visible light - that which is detectable by the human eye - consists of wavelengths ranging from approximately 780 nanometer (7.80 x 10-7 m) down to 390 nanometer (3.90 x 10-7 m). Specific wavelengths within the spectrum correspond to a specific color based upon how humans typically perceive light of that wavelength. The long wavelength end of the spectrum corresponds to light that is perceived by humans to be red and the short wavelength end of the spectrum corresponds to light that is perceived to be violet. Other colors within the spectrum include orange, yellow, green and blue. The graphic below depicts the approximate range of wavelengths that are associated with the various perceived colors within the spectrum.

Color Cones Color can be thought of as a psychological and physiological response to light waves of a specific frequency or set of frequencies impinging upon the eye. An understanding of the human response to color demands that one understand the biology of the eye. Light that enters the eye through the pupil ultimately strikes the inside surface of the eye known as the retina. The retina is lined with a variety of light sensing cells known as rods and cones. While the rods on the retina are sensitive to the intensity of light, they cannot distinguish between lights of different wavelengths. On the other hand, the cones are the color-sensing cells of the retina. When light of a given wavelength enters the eye and strikes the cones of the retina, a chemical reaction is activated that results in an electrical impulse being sent along nerves to the brain. It is believed that there are three kinds of cones, each sensitive to its own range of wavelengths within the visible light spectrum. These three kinds of cones are referred to as red cones, green cones, and blue cones because of their respective sensitivity to the wavelengths of light that are associated with red, green and blue.

Since the red cone is sensitive to a range of wavelengths, it is not only activated by wavelengths of red light, but also (to a lesser extent) by wavelengths of orange light, yellow light and even green light. In the same manner, the green cone is most sensitive to wavelengths of light associated with the color green. Yet the green cone can also be activated by wavelengths of light associated with the colors yellow and blue. The graphic below is a sensitivity curve that depicts the range of wavelengths and the sensitivity level for the three kinds of cones. The cone sensitivity curve shown above helps us to better understand our response to the light that is incident upon the retina. While the response is activated by the physics of light waves, the response itself is both physiological and psychological. Suppose that white light - i.e., light consisting of the full range of wavelengths within the visible light spectrum - is incident upon the retina. Upon striking the retina, the physiological occurs: photochemical reactions occur within the cones to produce electrical impulses that are sent along nerves to the brain.

The cones respond to the incident light by sending a message forward to brain, saying, "Light is hitting me." Upon reaching the brain, the psychological occurs: the brain detects the electrical messages being sent by the cones and interprets the meaning of the messages. The brain responds by saying "it is white." For the case of white light entering the eye and striking the retina, each of the three kinds of cones would be activated into sending the electrical messages along to the brain. And the brain recognizes that the messages are being sent by all three cones and somehow interprets this to mean that white light has entered the eye. Now suppose that light in the yellow range of wavelengths (approximately 577 nm to 597 nm) enters the eye and strikes the retina. Light with these wavelengths would activate both the green and the red cones of the retina. Upon striking the retina, the physiological occurs: electrical messages are sent by both the red and the green cones to the brain. Once received by the brain, the psychological occurs: the brain recognizes that the light has activated both the red and the green cones and somehow interprets this to mean that the object is yellow.

In this sense, the yellow appearance of objects is simply the result of yellow light from the object entering our eye and stimulating the red and the green cones simultaneously. If the appearance of yellow is perceived of an object when it activates the red and the green cones simultaneously, then what appearance would result if two overlapping red and green spotlights entered our eye? Using the same three-cone theory, we could make some predictions of the result. Red light entering our eye would mostly activate the red color cone; and green light entering our eye would mostly activate the green color cone. Each cone would send their usual electrical messages to the brain. If the brain has been psychologically trained to interpret these two signals to mean "yellow", then the brain would perceive the overlapping red and green spotlights to appear as yellow. To the eye-brain system, there is no difference in the physiological and psychological response to yellow light and a mixing of red and green light. The brain has no means of distinguishing between the two physical situations. In a technical sense, it is really not appropriate to refer to light as being colored. Light is simply a wave with a specific wavelength or a mixture of wavelengths; it has no color in and of itself.

An object that is emitting or reflecting light to our eye appears to have a specific color as the result of the eye-brain response to the wavelength. So technically, there is really no such thing as yellow light. Rather, there is light with a wavelength of about 590 nm that appears yellow. And there is also light with a mixture of wavelengths of about 700 nm and 530 nm that together appears yellow. The yellow appearance of these two clearly different light sources can be traced to the physiological and psychological response of the eye-brain system, and not to the light itself. So to be technically appropriate, a person would refer to "yellow light" as "light that creates a yellow appearance." Yet, to maintain a larger collection of friendships, a person would refer to "yellow light" as "yellow light." In the next several sections of Lesson 2, we will explore these concepts further by introducing three primary colors of light and generating some simple rules for predicting the color appearance of objects in terms of the three primary colors. Investigate! In this lesson we will spend a lot of time discussing three light colors - red, green, and blue. We will perceive light as consisting of red, green and blue qualities.

Use the RGB widget below to determine the ratios by which red, green and blue light combine to form other light colors. Enter the name of a color (maize, purple, orange, sky blue, etc.) into the field. Then click the Submit button to find out its red, green, and blue components. The Electromagnetic and Visible Spectra Light Waves and Color - Lesson 2 - Color and Vision The Electromagnetic and Visible Spectra The Electromagnetic and Visible Spectra Blue Skies and Red Sunsets As discussed in Unit 10 of The Physics Classroom Tutorial , electromagnetic waves are waves that are capable of traveling through a vacuum. Unlike mechanical waves that require a medium in order to transport their energy, electromagnetic waves are capable of transporting energy through the vacuum of outer space. Electromagnetic waves are produced by a vibrating electric charge and as such, they consist of both an electric and a magnetic component. The precise nature of such electromagnetic waves is not discussed in The Physics Classroom Tutorial. Nonetheless, there are a variety of statements that can be made about such waves. Electromagnetic waves exist with an enormous range of frequencies. This continuous range of frequencies is known as the electromagnetic spectrum.

The entire range of the spectrum is often broken into specific regions. The subdividing of the entire spectrum into smaller spectra is done mostly on the basis of how each region of electromagnetic waves interacts with matter. The diagram below depicts the electromagnetic spectrum and its various regions. The longer wavelength, lower frequency regions are located on the far left of the spectrum and the shorter wavelength, higher frequency regions are on the far right. Two very narrow regions within the spectrum are the visible light region and the X-ray region. You are undoubtedly familiar with some of the other regions of the electromagnetic spectrum. Visible Light Spectrum The focus of Lesson 2 will be upon the visible light region - the very narrow band of wavelengths located to the right of the infrared region and to the left of the ultraviolet region. Though electromagnetic waves exist in a vast range of wavelengths, our eyes are sensitive to only a very narrow band. Since this narrow band of wavelengths is the means by which humans see, we refer to it as the visible light spectrum. Normally when we use the term "light," we are referring to a type of electromagnetic wave that stimulates the retina of our eyes. In this sense, we are referring to visible light, a small spectrum from the enormous range of frequencies of electromagnetic radiation.

This visible light region consists of a spectrum of wavelengths that range from approximately 700 nanometers (abbreviated nm) to approximately 400 nm. Expressed in more familiar units, the range of wavelengths extends from 7 x 10-7 meter to 4 x 10-7 meter. This narrow band of visible light is affectionately known as ROYGBIV. Each individual wavelength within the spectrum of visible light wavelengths is representative of a particular color. That is, when light of that particular wavelength strikes the retina of our eye, we perceive that specific color sensation. Isaac Newton showed that light shining through a prism will be separated into its different wavelengths and will thus show the various colors that visible light is comprised of. The separation of visible light into its different colors is known as dispersion. Each color is characteristic of a distinct wavelength; and different wavelengths of light waves will bend varying amounts upon passage through a prism. For these reasons, visible light is dispersed upon passage through a prism. Dispersion of visible light produces the colors red (R), orange (O), yellow (Y), green (G), blue (B), and violet (V). It is because of this that visible light is sometimes referred to as ROY G.

BIV. (Incidentally, the indigo is not actually observed in the spectrum but is traditionally added to the list so that there is a vowel in Roy's last name.) The red wavelengths of light are the longer wavelengths and the violet wavelengths of light are the shorter wavelengths. Between red and violet, there is a continuous range or spectrum of wavelengths. The visible light spectrum is shown in the diagram below. When all the wavelengths of the visible light spectrum strike your eye at the same time, white is perceived. The sensation of white is not the result of a single color of light. Rather, the sensation of white is the result of a mixture of two or more colors of light. Thus, visible light - the mix of ROYGBIV - is sometimes referred to as white light. Technically speaking, white is not a color at all - at least not in the sense that there is a light wave with a wavelength that is characteristic of white. Rather, white is the combination of all the colors of the visible light spectrum. If all the wavelengths of the visible light spectrum give the appearance of white, then none of the wavelengths would lead to the appearance of black. Once more, black is not actually a color.

Technically speaking, black is merely the absence of the wavelengths of the visible light spectrum. So when you are in a room with no lights and everything around you appears black, it means that there are no wavelengths of visible light striking your eye as you sight at the surroundings. Investigate! The widget below matches the wavelength of light (in nanometers) to a particular color of light. Explore by entering various values between 400 nanometers and 700 nanometers. Values outside this range are not visible and therefore not associated with human-perceived color. Visible Light About Watch and Favorite Watch Watching this resources will notify you when proposed changes or new versions are created so you can keep track of improvements that have been made. Favorite Favoriting this resource allows you to save it in the “My Resources” tab of your account. There, you can easily access this resource later when you’re ready to customize it or assign it to your students. Visible Light Visible light is the portion of the electromagnetic spectrum that is visible to the human eye, ranging from roughly 390 to 750 nm.

Learning Objective Distinguish six ranges of the visible spectrum Key Points Visible light is produced by vibrations and rotations of atoms and molecules, as well as by electronic transitions within atoms and molecules. We say the atoms and molecules are excited when they absorb and relax when they emit through electronic transitions. This figure shows the visible part of the spectrum , together with the colors associated with particular pure wavelengths . Red light has the lowest frequencies and longest wavelengths, while violet has the highest frequencies and shortest wavelengths. Colors that can be produced by visible light of a narrow band of wavelengths are called pure spectral colors . They can be delineated roughly in wavelength as: violet (380-450 nm), blue (450-495 nm), green (495-570 nm), yellow (570-590 nm), orange (590-620 nm), and red (620 to 750 nm). Visible wavelengths pass through the optical window , the Earth's atmosphere allows this region of the electromagnetic spectrum to pass through largely unattenuated (see opacity plot in.

The portion of the EM spectrum used by photosynthesic organisms is called the photosynthetically active region (PAR) and corresponds to solar radiation between 400 and 700 nm, substantially overlapping with the range of human vision. Terms optical window the optical portion of the electromagnetic spectrum that passes through the atmosphere all the way to the ground. The window runs from around 300 nanometers (ultraviolet-C) at the short end up into the range the eye can use, roughly 400-700 nm and continues up through the visual infrared to around 1100 nm, which is thermal infrared. spectral color a color that is evoked by a single wavelength of light in the visible spectrum, or by a relatively narrow band of wavelengths. Every wavelength of light is perceived as a spectral color, in a continuous spectrum; the colors of sufficiently close wavelengths are indistinguishable. Full Text Visible Light Visible light, as called the visible spectrum, is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye. Electromagnetic radiation in this range of wavelengths is often simply referred to as "light".

A typical human eye will respond to wavelengths from about 390 to 750 nm (0.39 to 0.75 µm). In terms of frequency, this corresponds to a band in the vicinity of 400–790 THz. A light-adapted eye generally has its maximum sensitivity at around 555 nm (540 THz), in the green region of the optical spectrum. The spectrum does not, however, contain all the colors that the human eyes and brain can distinguish. Unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can be made only by a mix of multiple wavelengths. The electromagnetic spectrum, showing the major categories of electromagnetic waves. The range of frequencies and wavelengths is remarkable. The dividing line between some categories is distinct, whereas other categories overlap. Microwaves encompass the high frequency portion of the radio section of the EM spectrum. Visible light is produced by vibrations and rotations of atoms and molecules, as well as by electronic transitions within atoms and molecules. The receivers or detectors of light largely utilize electronic transitions. We say the atoms and molecules are excited when they absorb and relax when they emit through electronic transitions.

A small part of the electromagnetic spectrum that includes its visible components. The divisions between infrared, visible, and ultraviolet are not perfectly distinct, nor are those between the seven rainbow colors. The figure above shows this part of the spectrum, together with the colors associated with particular pure wavelengths. Red light has the lowest frequencies and longest wavelengths, while violet has the highest frequencies and shortest wavelengths. Blackbody radiation from the Sun peaks in the visible part of the spectrum but is more intense in the red than in the violet, making the Sun yellowish in appearance. Colors that can be produced by visible light of a narrow band of wavelengths (monochromaticlight) are called pure spectral colors. Quantitatively, the regions of the visible spectrum encompassing each spectral color can be delineated roughly as: red - 620 to 750 nm (400-484 THz) Note that each color can come in many shades, since the spectrum is continuous. The human eye is insensitive to electromagnetic radiation outside this range. By definition any images presented with data recorded from wavelengths other than those in the visible part of the spectrum (such as IR images of humans or animals or astronomical X-ray images) are necessarily in false color.

Visible Light and Earth's Atmosphere Visible wavelengths pass through the "optical window", the region of the electromagnetic spectrum which allows wavelengths to pass largely unattenuated through the Earth's atmosphere (see opacity plot in. An example of this phenomenon is that clean air scatters blue light more than red wavelengths, and so the midday sky appears blue. This is a plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation. Most UV wavelengths are absorbed by oxygen and ozone in Earth's atmosphere. Observations of astronomical UV sources must be done from space. The optical window is also called the visible window because it overlaps the human visible response spectrum. This is not coincidental as humanity's ancestors evolved vision that could make use of the most plentiful wavelengths of light.The near infrared (NIR) window lies just out of the human vision, as well as the Medium Wavelength IR (MWIR) window and the Long Wavelength or Far Infrared (LWIR or FIR) window though other animals may experience them. A consequence of the existence of the optical window in Earth's atmosphere is the relatively balmy temperature conditions on Earth's surface.

The Sun's luminosity function peaks in the visible range and light in that range is able to travel to the surface of the planet unattenuated due to the optical window. This allows visible light to heat the surface. The surface of the planet then emits energy primarily in infrared wavelengths, which has much greater difficulty escaping (and thus causing the planet to cool) due to the opacity of the atmosphere in the infrared. Earth's surface would be much cooler without this effect. Photosynthesis Plants, like animals, have evolved to utilize and respond to parts of the electromagnetic spectrum they are embedded in. Plants (and many bacteria) convert the light energy captured from the Sun into chemical energy that can be used to fuel the organism's activities. In plants, algae, and cyanobacteria, photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product. Photosynthesis is vital for all aerobic life on Earth (such as humans and animals). The portion of the EM spectrum used by photosynthesic organisms is called the photosynthetically active region (PAR) and corresponds to solar radiation between 400 and 700 nm, substantially overlapping with the range of human vision.

This is again not coincidental; the light in this range is the most plentiful to organisms on the surface of Earth because the Sun emits about half of its luminosity in this wavelength range and it is allowed to pass freely through the optical windows in Earth's atmosphere. Reading on Color & Light, Part I Color and Light Here we ask how color is sensed by the viewer. To answer the question we need to specify how color is described and how color information is received by the eye. The starting point of an understanding of color is a description of light. Light: Photons and Waves Isaac Newton discovered in 1672 that light could be split into many colors by a prism, and used this experimental concept to analyze light. The colors produced by light passing through a prism are arranged in a precise array or spectrum from red through orange, yellow, green, blue, indigo and into violet. The students' memory trick is to recall the name "Roy G. Biv" where each letter represents a color. The order of colors is constant, and each color has a unique signature identifying its location in the spectrum. The signature of color is the wavelength of light. Fig. 1.

The electromagnetic spectrum, which encompasses the visible region of light, extends from gamma rays with wave lengths of one hundredth of a nanometer to radio waves with wave lengths of one meter or greater. Somewhat less than 100 years after Newton's discoveries, James Clerk Maxwell showed that light was a form of electromagnetic radiation . This radiation contains radio waves, visible light and X-rays. Figure 1 shows electromagnetic radiation as a spectrum of radiation extending beyond the visible radiation to include at one end radio waves and at the other end gamma rays. The visible light region occupies a very small portion of the electromagnetic spectrum. The light emitted by the sun falls within the visible region and extends beyond the red (into the infrared, IR) and the ultraviolet (UV) with a maximum intensity in the yellow. When we consider light as an electromagnetic wave, a color's spectral signature may be identified by noting its wavelength. We sense the waves as color, violet being the shortest wavelength and red the longest. Visible light is the range of wavelengths within the electromagnetic spectrum that the eye responds to. Although radiation of longer or shorter wavelengths are present, the human eye is not capable of responding to it. Figure 2.

A wave representation of three different light hues: red, yellow-green and violet, each with a different wavelength , which represents the distance between wave crests. Three typical waves of visible light are shown in Fig. 2. The wavelength is the distance from one wave crest to the next, and is represented by the Greek letter lambda, λ. Violet light is electromagnetic radiation with wavelengths of 410 nanometers and red light has a wavelength of 680 nanometers. The nanometer is a unit of distance in the metric scale and is abbreviated as nm. One nanometer (nm) equals one thousand millionths of a meter (m) or 1 nm = 10-9 m. One nanometer is a distance too small to be resolved in an optical microscope but one micron (�m) or one thousand nanometers can be resolved (1 micron = 1000 nm). The wavelengths of visible light are smaller than common objects such as the thickness of a sheet of paper or the diameter of a human hair. Both of these are about one hundred microns thick which translates to distances greater than one hundred wavelengths of visible light.

As we move through the visible spectrum of violet, blue, green, yellow, orange and red, the wavelengths become longer. The range of wavelengths (400 - 700 nm) of visible light is centrally located in the electromagnetic spectrum (Fig. 1). Infrared and radio waves are at the long wavelength side while ultraviolet (UV), x-rays and gamma rays lie at the short wavelength side of the electromagnetic spectrum. Radiation with wavelengths shorter than 400 nm cannot be sensed by the eye. Light with wavelength longer than 700 nanometers is also invisible. We can describe light as electromagnetic waves with color identified by its wavelength. We can also consider light as a stream of minute packets of energy-photons - which create a pulsating electromagnetic disturbance. A single photon of one color differs from a photon of another color only by its energy. In the description of light, the most convenient unit of energy to use is the electron volt, abbreviated eV. The electron volt is the energy gained by an electron that moves across a positive voltage of one volt (V).

For example 1.5 electron volts is the energy gained by an electron moving from a negative metal plate to a positive plate which are connected to the terminals of a common 1.5 volt "C" battery. Visible light is composed of photons in the energy range of around 2 to 3 eV (Fig. 3). As the energy of the light increases, the wavelength decreases. Orange light with a wavelength of 620 nanometers is composed of photons with energy of 2 eV. It is the energy range of 1.8 to 3.1 eV which triggers the photo receptors in the eye. Lower energies (longer wavelengths) are not detected by the human eye but can be detected by special infrared sensors. Higher energies (shorter wavelengths) such as x-rays are detected by x-ray sensitive photographic film or again by special devices. Figure 3. Diagram showing the visible region of the electromagnetic spectrum in terms of wavelength and corresponding energies. The visible region extends from 400 nm to 700 nm (wavelength) with corresponding energies of 3.1 to 1.8 electron volts (eV). Light rays are composed of photons whose energy specifies a color from red to violet.

The intensity or brightness of the light is defined by the flux, or number of photons passing through a unit area in a unit time; i.e., number of photons per cm2 per sec. If we specify a wavelength in the visible range on the electromagnetic scale, we can attribute a color to it. That is, laser light with a single wavelength of 650 nanometers looks red. We show the major spectral colors in Fig. 4a as a linear sequence from red (at 700mm) to violet at 400 nm. A circular sequence of these same spectral colors, the color wheel first attributed to Isaac Newton, is shown in Fig. 4b. The progression of colors from red through violet is identical to that on the linear scale. The circular wavelength scale outside the color wheel shows the wavelength connection between the linear and circular sequences. The purple region in the color wheel is a notable difference between the two sequences. Colors in this purple portion of the color wheel are composed of mixtures of wavelength and cannot be represented by a single wavelength. Figure 4. The region of visible light in wavelengths shown as a linear arrangement (a) and as a circle (b) as conceived by Sir Isaac Newton.

The color purple shown in the color wheel (b) is composed of a mixture of light in the red and violet regions of the spectrum. Purple cannot be represented by a single wavelength of light. No single wavelength exists for the color brown just as none exists for purple. Purple can be created with a mixture of wavelengths in both the red and the violet. Brown requires a more complex mixture of wavelengths from at least three regions of the sequence. The Color of Objects Here we consider the color of an object illuminated by white light. Color is produced by the absorption of selected wavelengths of light by an object. Objects can be thought of as absorbing all colors except the colors of their appearance which are reflected as illustrated in Fig. 5. A blue object illuminated by white light absorbs most of the wavelengths except those corresponding to blue light. These blue wavelengths are reflected by the object. Figure 5. White light composed of all wavelengths of visible light incident on a pure blue object. Only blue light is reflected from the surface. The Eye and Color Sensation Our perception of color arises from the composition of light - the energy spectrum of photons - which enter the eye. The retina on the inner surface of the back of the eye (Fig. 6) contains photosensitive cells.

These cells contain pigments which absorb visible light. Of the two classes of photosensitive cells, rods and cones, it is the cones that allow us to distinguish between different colors. The rods are effective in dim light and sense differences in light intensity - the flux of incident photons - not photon energy. So in dim light we perceive colored objects as shades of grey, not shades of color. Figure 6. A cross-sectional representation of the eye showing light entering through the pupil. The photosensitive cells, cones and rods, are located in the retina: cones respond to color and rods respond to light intensity. Color is perceived in the retina by three sets of cones which are photoreceptors with sensitivity to photons whose energy broadly overlaps the blue, green and red portions of the spectrum. Color vision is possible because the sets of cones differ from each other in their sensitivity to photon energy. The sensitivity of the cones to light of the same intensity (the same photon flux) but different wavelengths (energy) is shown in Fig. 7. The maximum sensitivity is to yellow light, but cone R has a maximum in the red-orange, G in the green-yellow, and B in the blue. The sensitivities of the three comes overlap.

For every color signal or flux of photons reaching the eye, some ratio of response within the three types of cones is triggered. It is this ratio that permits the perception of a particular color. Figure 7. The response of the tree cones to incident light: cone R (pigment R) has a maximum sensitivity in the orange-red, cone G (pigment G) in the green-yellow, and cone B (pigment B) in the blue portions of the visible spectrum. The sensitivities of the three cones overlap and the perceived color is due to the relative response of the three cones. Wavelength Range of Visible Light Wavelength Range of Visible Light Result Curtis, Barnes. Invitation to Biology: Fifth Edition. New York: Worth Publishers, 1994: 163. "For the human eye, the visible radiations range from violet light, in which the shortest rays are about 380 nanometers, to red light, in which the longest rays are about 750 nanometers." 380–750 nm Chambers Cambridge. Chambers Science & Technology Dictionary. New York: W & R Chambers Limited, 1940: 914.

"light [OPTICS] Electromagnetic radiation with wavelengths capable of causing the sensation of vision, ranging approximately from 4000 (extreme violet) to 7700 angstroms (extreme red)." 400–770 nm Freudenrich, Craig. How Light Works . Howstuffworks.com "The wavelengths of the light we can see range from 400 to 700 billionths of a meter." 400–700 nm Lapedes, Daniel. Dictionary of Scientific & Technical Terms: Second Edition. New York: McGraw Hill, 1978: 954. "visible radiation(Phys.).Electromagnetic radiation which falls within the wavelength range of 780 to 380 nm, over which the normal eye is sensitive." 380–780 nm Cesare, Emiliani. Dictionary of the Physical Sciences. New York: Oxford University Press, 1987: 124. "light1.

Visible electromagnetic radiation (λ = 0.40 to 0.72 Ωm)." 400–720 nm Human beings posses five senses, which include the ability to see, hear, taste smell and feel. The ability to see is by far the most important of the five. Sight allows us to differentiate between things, to know when something is moving towards us or away from us and to react to hazardous conditions before they cause any harm. The ability to see also accounts for that awe we get while looking at the sunset over the blue ocean waters of the white sandy beaches with plenty of tall palm trees and waterfalls and not another being in sight. Our eyes are what allow us to see. Our eyes are designed to detect a small portion of the electromagnetic spectrum. This part of the spectrum is called the visible light region. The visible light region ranges in wavelengths from about 380 or 400 nm to 700 or 780 nm depending on which source is used. In fact it also depends on the sensitivity of a specific persons eyes. Light waves travel at very high speeds and are absorbed or reflected by various objects.

If all the waves are absorbed and none reach our eye then we do not see anything and the image before us appears as having the color of black. If the object reflects all wavelengths of light equally then the object appears to be the color of white. If an object on the other hand reflects light of certain wavelengths but absorbs others then the color of the object will match the wavelengths that are reflected. Every wavelength of light corresponds to a color which was assigned by people for easier recognition. The longer wavelengths appear as red while the shorter visible wavelengths appear as blue or violet. Pavel Borodulin -- 2002 External links to this page: US Patent 7,561,332 , Applications and fabrication techniques for large scale wire grid polarizers, Michael J. Little, et al. 2009 What Wavelength Goes With a Color? Contact Us What Wavelength Goes With a Color? Our eyes are sensitive to light which lies in a very small region of the electromagnetic spectrum labeled "visible light". This "visible light" corresponds to a wavelength range of 400 - 700 nanometers (nm) and a color range of violet through red.

The human eye is not capable of "seeing" radiation with wavelengths outside the visible spectrum. The visible colors from shortest to longest wavelength are: violet, blue, green, yellow, orange, and red. Ultraviolet radiation has a shorter wavelength than the visible violet light. Infrared radiation has a longer wavelength than visible red light. The white light is a mixture of the colors of the visible spectrum. Black is a total absence of light. Earth's most important energy source is the Sun. Sunlight consists of the entire electromagnetic spectrum. Learn more: Violet Light The visible violet light has a wavelength of about 400 nm. Within the visible wavelength spectrum, violet and blue wavelengths are scattered more efficiently than other wavelengths. The sky looks blue, not violet, because our eyes are more sensitive to blue light (the sun also emits more energy as blue light than as violet). The visible indigo light has a wavelength of about 445 nm. Blue Light The visible blue light has a wavelength of about 475 nm. Because the blue wavelengths are shorter in the visible spectrum, they are scattered more efficiently by the molecules in the atmosphere.

This causes the sky to appear blue during the main part of the day, when blue light is scattered into your eye no matter which direction you look. Green Light The visible green light has a wavelength of about 510 nm. Grass, for example, appears green because all of the colors in the visible part of the spectrum are absorbed into the leaves of the grass except green. Green is reflected, therefore grass appears green. The visible orange light has a wavelength of about 590 nm. Low-pressure sodium lamps, like those used in some parking lots, emit a orange-ish (wavelength 589 nm) light. Red Light The visible red light has a wavelength of about 650 nm. At sunrise and sunset, the light you see has traveled a longer distance through the atmosphere. A large amount of blue and violet light has been removed as a result of scattering and the longwave colors, such as red and orange, are more readily seen. There are many wavelengths in the electromagnetic spectrum the human eye cannot detect. Energy with wavelengths too short for humans to see Energy with wavelengths too short to see is "more violet than violet". Light with such short wavelengths is called "Ultraviolet" light.

The term "ultra-" means higher than. How do we know this light exists? One way is that this kind of light causes sunburns. Our skin is sensitive to this kind of light. If we stay out in this light without sunblock protection, our skin absorbs this energy. After the energy is absorbed, it can make our skin change color ("tan") or it can break down the cells and cause other damage. Energy with wavelengths too long for humans to see Energy whose wavelength is too long to see is "redder than red". Light with such long wavelengths is called "Infrared" light. The term "Infra-" means "lower than". How do we know this kind of light exists? One way is that we can feel energy with these wavelengths such as when we sit in front of a campfire or when we get close to a stove burner. Scientists like Samuel Pierpont Langley passed light through a prism and discovered that the infrared light the scientists could not see beyond red could make other things hot. Very long wavelengths of infrared light radiate heat to outer space. This radiation is important to the Earth's energy budget. If this energy did not escape to space, the solar energy that the Earth absorbs would continue to heat the Earth.

Visible Light - Mission:Science Visible Light National Aeronautics and Space Administration, Science Mission Directorate. (2010). Visible Light. Retrieved , from Mission:Science website: Science Mission Directorate. "Visible Light" Mission:Science. 2010. National Aeronautics and Space Administration. WAVELENGTHS OF VISIBLE LIGHT All electromagnetic radiation is light, but we can only see a small portion of this radiation—the portion we call visible light. Cone-shaped cells in our eyes act as receivers tuned to the wavelengths in this narrow band of the spectrum. Other portions of the spectrum have wavelengths too large or too small and energetic for the biological limitations of our perception. As the full spectrum of visible light travels through a prism, the wavelengths separate into the colors of the rainbow because each color is a different wavelength. Violet has the shortest wavelength, at around 380 nanometers, and red has the longest wavelength, at around 700 nanometers. Isaac Newton's experiment in 1665 showed that a prism bends visible light and that each color refracts at a slightly different angle depending on the wavelength of the color.

Credit: Troy Benesch Each color in a rainbow corresponds to a different wavelength of electromagnetic spectrum. THE SUN'S CORONA The Sun is the dominant source for visible-light waves our eyes receive. The outer-most layer of the Sun's atmosphere, the corona, can be seen in visible light. But it is so faint it cannot not be seen except during a total solar eclipse because the bright photosphere overwhelms it. The photograph below was taken during a total eclipse of the Sun where the photosphere and chromosphere are almost completely blocked by the moon. The tapered patterns—coronal streamers—around the Sun are formed by the outward flow of plasma that is shaped by magnetic field lines extending millions of miles into space. Credit: © 2008 Miloslav Druckmüller, Martin Dietzel, Peter Aniol, Vojtech Rušin COLOR AND TEMPERATURE As objects grow hotter, they radiate energy dominated by shorter wavelengths, changing color before our eyes. A flame on a blow torch shifts from reddish to bluish in color as it is adjusted to burn hotter. In the same way, the color of stars tells scientists about their temperature.

Our Sun produces more yellow light than any other color because its surface temperature is 5,500°C. If the Sun's surface were cooler—say 3,000°C—it would look reddish, like the star Betelgeuse. If the Sun were hotter—say, 12,000°C—it would look blue, like the star Rigel. Isaac Newton's experiment in 1665 showed that a prism bends visible light and that each color refracts at a slightly different angle depending on the wavelength of the color. Credit: Jenny Mottar; Image Courtesy of SOHO/consortium. The High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter (MRO) captured this spectacular visible light image of Victoria Crater. Credit: NASA/JPL/University of Arizona SPECTRA AND SPECTRAL SIGNATURES Close examination of the visible-light spectrum from our Sun and other stars reveals a pattern of dark lines—called absorption lines. These patterns can provide important scientific clues that reveal hidden properties of objects throughout the universe. Certain elements in the Sun's atmosphere absorb certain colors of light. These patterns of lines within spectra act like fingerprints for atoms and molecules.

Looking at the Sun's spectrum, for example, the fingerprints for elements are clear to those knowledgeable about those patterns. Patterns are also evident in a graph of an object's reflectance. Elements, molecules, and even cell structures have unique signatures of reflectance. A graph of an object's reflectance across a spectrum is called a spectral signature. Spectral signatures of different Earth features within the visible light spectrum ARE shown below. Credit: Jeannie Allen ACTIVE REMOTE SENSING—ALTIMETRY Laser altimetry is an example of active remote sensing using visible light. NASA's Geoscience Laser Altimeter System (GLAS) instrument onboard the Ice, Cloud, and land Elevation Satellite (ICESat) enabled scientists to calculate the elevation of Earth's polar ice sheets using lasers and ancillary data. Changes in elevation over time help to estimate variations in the amount of water stored as ice on our planet. The image below shows elevation data over the West Antarctic Ice Streams. Laser altimeters can also make unique measurements of the heights and characteristics of clouds, as well as the top and structure of the vegetation canopy of forests. They can also sense the distribution of aerosols from sources such as dust storms and forest fires.

Credit: NASA/Goddard Space Flight Center

Question: What color consists of the longest wavelengths of lights visible by the human eye?
Answer: Red